What do you know
about STARS?

The Milky Way as seen from space

How many stars are there in the Milky Way Galaxy?




200 million


200 billion

Nope. Try again!
You got it!

ANSWER: 200 billion

Our Sun is one of more than 200 billion (200,000,000,000) stars in the Milky Way Galaxy . Every individual star that you can see with the naked eye is in the Milky Way. We can observe more than 100 billion other galaxies  beyond the Milky Way.

Question 1 of 10
star cluster

Most stars form in tightly packed groups called:


star clusters


star huddles


star formations

Nope. Try again!
You got it!

ANSWER: star clusters

Our star, the Sun, was born, along with hundreds to thousands of other stars in a star cluster. As with many young stars, the Sun was ejected from its cluster. Since then it has traveled, along with its planets, in orbit around the center of the Milky Way.

Question 2 of 10

A star's mass  is the most important thing that determines:


its temperature, luminosity, and color


how it will live and die


all of the above

Nope. Try again!
You got it!

ANSWER: all of the above

The more massive a star is, the hotter it burns. The hotter it burns, the faster a star uses up its fuel and the shorter its life is. The hottest and most massive stars are blue and bright. The coolest and least massive stars are red and dim.

Question 3 of 10
a. (left). red giant (artist rendering) and b. (right) white dwarf

How do most stars end their lives?


The outer layer swells, and the star becomes a red giant.


The core shrinks, and the star becomes a white dwarf.


First a, then b.

Nope. Try again!
You got it!

ANSWER: First a, then b.

Most dying stars—including our Sun—will become red giants, then white dwarfs. It takes billions of years for the white dwarfs to cool down and fade away. 99% of stars end their lives like this.

Question 4 of 10
Early flash of a supernova

At the end of its life, a very massive star will run out of fuel and explode as a:







Nope. Try again!
You got it!

ANSWER: supernova

It's very rare for a star to "go supernova." Only about 1% of stars are massive enough to explode as one. Supernovas occur somewhere in the Milky Way Galaxy once every 50-100 years on average.

Question 5 of 10

How does our star, the Sun , compare to other stars?


more massive than average


close to average


less massive than average

Nope. Try again!
You got it!

ANSWER: more massive than average

Surprise! The Sun is not your average star. It is a middle-aged yellow star that is more massive than nearly 90% of stars.

Question 6 of 10

The Sun contains what percentage of the Solar System's mass?







Nope. Try again!
You got it!

ANSWER: 98.6%

Our Sun is the hulk of our Solar System . The other 1.4% is in the planets, moons, asteroids, comets, gas, and dust that orbit the Sun.

Question 7 of 10
Earth and Sun as seen from space

About how long does the Sun's light  take to reach Earth?


8 minutes


8 hours


8 months

Nope. Try again!
You got it!

ANSWER: 8 minutes

Light travels incredibly fast—at a speed of 186,000 miles per second. Sunlight reaches us about 8 minutes after it leaves the Sun. A light-year  is the distance light travels in one year.

Question 8 of 10

How long does it take our Solar System to orbit the center of the Milky Way Galaxy?


25,000 years


250,000 years


250 million years

Nope. Try again!
You got it!

ANSWER: 250 million years

It takes one "Galactic Year," or 250 million years, for our Solar System to circle the center of the spiral-shaped galaxy once. Dinosaurs first appeared about one Galactic Year ago! The Earth formed 18 Galactic Years ago.

Question 9 of 10
Space with high density of stars from the Global Cluster 56

Around the world today, astronomers observe stars using telescopes :


on Earth


in space


on Earth and in space

Nope. Try again!
You got it!

ANSWER: on Earth and in space

To study stars near and far, astronomers analyze their light using telescopes on Earth and in space. In the universe as far as our telescopes can ever see, there are perhaps 20,000,000,000,000,000,000,000 stars! Or more.

Question 10 of 10
Nice try! Not bad! Stellar! A star-studded score! You got out of 10 right on the first guess.
Image Credits:

Milkyway, NASA/JPL-Caltech; Christmas Tree Cluster; NASA//JPL-Caltech/P.S. Teixeira (Center for Astrophysics); exploding star’s shockwave, NASA Ames/W. Stenzel; 4b white dwarf star, NASA, ESA, H. Bond (STScI) and M. Barstow (University of Leicester); 9. Sun and Earth, NASA Goddard Space Flight Center; globular cluster Messier 56, NASA & ESA;